critical swim speed (CSS)
CSS training is a simple way to improve swim fitness, pacing and muscular endurance. It can also motivate athletes as a method to measure improvement in swim fitness throughout the season.
Many triathletes are left frustrated when their dedication in the pool does not pay off on race day. Despite hours of training, they only see small gains. One type of triathlete may consistently swim for hours each week with excellent endurance but only has one pace for all sessions. On the flipside, is the lifelong pool swimmer who is incredibly fast and strong in training sessions, yet struggles to gain race-specific endurance. Though these athletes are much different, CSS training is the answer for both to see the improvements they have worked so hard for!
What Exactly is Critical Swim Speed?
Similar to how an FTP or LT Test can help you establish zones for running and biking, the CSS test does the same for swimming. Zones allow the athlete to dial in their intensity so they can perform optimally for the distance of their event. In theory, CSS pace is what you could sustain for a 1500 time trial (thankfully without having to actually do a 1500 time trial)!
Keep in mind that CSS is endurance race-specific training. It is not used for individuals hoping to improve speed for short distances, but it will teach you to sustain a moderately high speed for a longer distance.
How to Perform a CSS Test
The CSS test includes a 400 and a 200 time trial swim (meters or yards). Before attempting these swims perform a thorough warm-up where your effort increases throughout the set with the final effort being at 100% – get you used to swimming fast!
Warm-up (600)
200 easy freestyle
4×50 freestyle (25 fast, 25 easy) with 10-sec rest interval
200 easy
100 build speed
Main Set TEST (800)
400 time trial (record time)
200 easy with time on the wall (5-8 min total)
200 time trial (record time)
Cool Down
200-1000 easy (feel free to extend cool down)